1. Field of the Invention
This invention relates to titanium carbide whiskers, and more particularly, it relates to an improved process for producing titanium carbide whiskers.
2. Description of the Related Art
In related art, there is disclosed different method of producing titanium carbide whiskers. For example, German Patentschrift 111550 discloses forming titanium carbide whiskers from a heterogeneous alloy which is melted and caused to solidify using directional solidification techniques to form the whiskers. After formation of the whiskers, the matrix is dissolved to recover the whiskers.
Japanese Patent Document 59-45638 discloses the formation of titanium carbide whiskers by first dipping a carbonaceous base in an aqueous solution of a noble metal such as platinum chloride and then drying the base. The base material is then heated in an atmosphere of hydrogen and a mixed gas of a volatile titanium halide and CO is supplied to deposit and grow the titanium carbide whiskers on the surface of the base material.
Higashi et al, in "Crystal Growth of Borides and Carbides of Transition Metals from Molten Aluminum Solutions", disclose the growth of single crystals of borides and carbides of Group IVA, VA, VIA metals and Mn (Group VIIA) using a molten aluminum solvent.
Kadota et al, in "Growth of Titanium Carbide Whiskers and Measurements of their Mechanical Properties", describes the growth of titanium carbide whiskers on a graphite substrate at 1250.degree. C. by CVD using TiCl.sub.4, CO, and H.sub.2.
Kato et al, in "Growth Rate of Titanium Carbide Whiskers in Chemical Vapor Deposition", teach the growth of titanium carbide whiskers from a TiCl.sub.4 -H.sub.2 -CH.sub.4 system using graphite plates and mullite tubes as the substrates. The authors state that polyhedral microcrystallites were deposited when graphite was used as the substrate but that the titanium carbide whiskers grew when a mullite tube was used as the substrate.
Kato et al, in "Some Common Aspects of the Growth of TiN, ZrN, TiC, and ZrC Whiskers in Chemical Vapor Deposition", discuss the effect of substrate on crystal growth of TiN, ZrN, TiC, and ZrC whiskers and the morphology and growth process of these whiskers.
Tamari et al, in "Catalytic Effects of Various Metals and Refractory Oxides on the Growth of TiC Whiskers by Chemical Vapor Deposition", describe the growth of TiC whiskers from the TiCl.sub.4 -H.sub.2 -CH.sub.4 system on various substrates including metals and metal oxides, including temperature effects and direction of whisker growth on particular substrates.
Wokulski et al, in "On the Growth and Morphology of TiC.sub.x Whiskers", disclose various growth conditions for growing TiC whiskers including mole ratios of Ti to C and temperature. The morphology, stoichiometry, and structure of the resulting whiskers is also discussed.
Wokulski et al, in "The Influence of Nickel on VLS Growth and Real Structure of TiC Whiskers", describe the use of nickel in a vapor-liquid-solid (VLS) mechanism to form titanium carbide whiskers in which liquid Ni-Ti-C alloy is formed from which the TiC whiskers grow.
The use of titanium carbide whiskers as reinforcement in carbonaceous material for industrial use is described in Hitachi Japanese patent J60137871 which discloses a carbonaceous material containing needle crystals of SiC, TiC, B.sub.4 C, and/or CaSiO.sub.3. Titanium carbide whiskers have also been used in the formation of lightweight titanium composite materials for aerospace as described by Saito in Japanese patent J6110734 wherein titanium powder and/or alloy is surface oxidized to form titanium oxide film on the particles which are then mixed with carbon and heated in air so that the film of titanium oxide is carburised to form titanium carbide whiskers.
However, there is still a great need for providing a method for controlling the growth and size of the TiC whiskers. The present invention fulfills that need by providing a process for producing TiC which is effective in providing TiC whiskers having very small diameter, e.g., 1 to 2 micrometers or less.